I have had couple 60'* Pontiacs but here is what i can scratch up quickly ...
1956 Star Chief Custom Catalina 124" wb ... ... i am assuming 2dr, HT
basket case to perfect ranges $1,200 - $30,000
there are other many models but prices similar with $25k
average high price and with convertible to $41,000.
These numbers are from OLD CARS PRICE GUIDE for stock models.
The engine and rarity issues need experts. Try Pontiac Oakland Club International
(great club for us older model owners)
Pontiac Production Numbers - 1956 Model Production Numbers
Star Chief 127,626 (from POCI website)
If you wanted to pay some money ($50) for exact info ... get the VIN and send to Pontiac Historical Services (PHS Historic Services
(Just read they have exact info on "1961 and newer". Sorry, they may still have something to help on the site.)
thoughts ... Vin and engine Vin matching started in 1969 I believe so, there is no way to verify matched engine and body except
for component date codes which can be kinda loose.
If it was built as a racer, the dual quad combo sounds like an add on since most oldies were tripowers for top street motors.
trivia alert ... first Bonneville was 1958 and could be a fuelie (fuel injection)
(perfect 58 fuelie convertible would be $100,000)
2005 Bonneville GXP – Dk Grey
2001 Grand Prix GTP
1994 Bonneville SSEi – * Port Magnuson SC
1969 Grand Prix SJ – 428cid/370hp